Undergraduate research is a ‘high-impact’ learning experience, where learners formulate their own questions about the Universe and figure out how best to approach learning about those questions. It gives a chance for learners to apply a wide range of important skills – reading primary literature, writing, visualization, computational techniques and statistical/mathematical techniques. Furthermore, research can be an interesting and engaging experience, and can help learners start to identify as scientists. But mostly, research is a way that many folk fall in love with the Universe and its many wonders and mysteries.

Accordingly, I have around a dozen undergraduates working with me on research projects. We currently use two datasets – resolved star datasets from the HST GHOSTS survey (our observational dataset) and the Illustris hydrodynamical simulation (our theoretical dataset). We practice ‘writing to learn’ by posting about our research on our blog (which requires permission to read and contribute to). Over the course of the fall and winter semesters, we work towards posters describing our research, which are given during the Astronomy department undergraduate poster fair in early April.

This page has assorted links and resources that are useful for the collaborators in the group.

Useful resources for intuition-building

• Chapters 25-29 of Astronomy (an open-source astronomy textbook) offer a broad and accessible introduction to galaxies and cosmology.
• For students who are more advanced, search for ‘Sparke and Gallagher pdf’ online; the organization isn’t necessarily ideal, but it offers a good overview of many classical ideas in the study of galaxies.
• I gave a talk in Saturday Morning Physics about this research.
• There are some articles that illustrate some of the ideas in stellar halos: observational – Martinez-Delgado et al. 2010 shows many different stellar streams, Monachesi et al. 2016 and Harmsen et al. 2017 (this is a paper from this undergraduate research group) discussing the metallicities and density profiles of stellar halos in our GHOSTS sample.
• Using stellar halo observations and models in concert to try to characterize the most massive merger event – rudimentary version by Bell et al. 2017, and a much more detailed discussion of M31’s most important merger by D’Souza & Bell 2018.

Python & Jupyter notebook resources

• Jake Vanderplas has a very pleasant ‘Whirlwind tour of Python’ that might help folks get oriented, with attached Jupyter notebooks. That link seems a little messy (you have to scroll down and then click on the individual chapters), but the advantage of it is that you can download the different ipython notebooks and work through them yourself – this is great, you can play with them, break them, learn from them. I recommend this to everyone in the group, at the level of 1-2 hours per week.
• If you’ve graduated from this, then the next step is his ‘Data science handbook’ – same deal. It’s terrific; I’m working my way through this.
• Where to download Python (via Anaconda) – please download Python 3.X

Resources for star cluster and dwarf galaxy discovery, analysis, and importance

• Papers where our group found dwarf galaxies : Slater et al. 2011, Bell et al. 2011 (these two were in SDSS, and are Andromeda satellites); Monachesi et al 2014 (this was an unexpectedly distant D~11Mpc star-forming dwarf projected close to M81 (D~3.5Mpc) on the sky, which is a warning against us using proximity alone as a reason to argue a low surface brightness fuzz near a big galaxy is automatically a dwarf satellite); Smercina et al. 2017, 2018 are using Subaru HSC with resolved stars to discover satellites and try to understand what they can tell us about how galaxies form in low-mass dark matter halos.
• The cosmological importance of dwarf galaxies : Moore et al. 1999 (the paper that got this whole thing started), Bullock and Boylan-Kolchin 2017 (an up-to-date review of the status of the cosmological import of dwarf galaxies, it’s a great place to find references for further study).
• Tools for interpreting dwarf galaxies : Streich et al. 2014 conversion from F606W-F814W color to metallicity, assuming that the stars are similarly ancient to nearby globular clusters (this may not be an awesome assumption, dwarf galaxies often have extended star formation histories).
• The distinction between dwarf galaxies and star clusters often becomes ambiguous when one reaches fainter systems : Willman & Strader 2012 (I’m actually not thrilled by their framing that detaches from CDM – as far as we can see the defining feature of a galaxy is that it has dark matter bound to it whereas a star cluster does not, so avoiding the thing that seems to be the primary difference seems perhaps an idea that confuses rather than clarifies. Nonetheless, it brings up a number of interesting issues). One example that is really relevant for us is Crater – Belokurov et al. 2014 vs. Laevens et al. 2014 discovery of the same object, with a satellite vs. diffuse globular cluster interpretation. It is round (which tends to make one think globular cluster, owing to 2-body relaxation), but extended. Laevens used stellar populations to make the decision – we don’t have access to that type of information, sadly.

Resources for gas and distant star formation in interacting groups

• M81’s spectacular HI tidal mess was first uncovered by Yun et al. 1994. There is a more comprehensive and accurate map, and much richer discussion in a recent de Blok et al. 2018 paper; their section 4.1 argues that star formation is only in the locally densest areas, which differs somewhat with what we have been discussing; we might well want to revisit this. The most up to date view of the stars in this system are described in Okamoto et al. 2015. Detailed HST-derived SFHs are in Weisz et al. 2008 for some M81 group satellites and two dense features in this map (the Garland and Ho IX).